Erica has actually fought in real boxing and Muay Thai events
Koldin is a very accomplished wrestler that actually comes from a family of wrestlers
Gabriella has actually competed and won many gold medals in Brazilian Jiu Jitsu and Free Style Wrestling.
The actors went through an actual fight camp to prepare for the movie. They all trained in Kickboxing and Brazilian Jiu Jitsu for 3-5 hours a day for over a month.
Skittles candy helped Gabriella centre herself after dramatic and emotional scenes.